The present invention relates to an anti-skid system for the driving wheels of a motor vehicle, the brake system of which comprises two hydraulic sub-circuits, each connecting a driving wheel and a free wheel to a working chamber of a master cylinder connected to a general reservoir of fluid under low pressure, and includes a wheel anti-lock braking device.
Such a system is described, for example, in DE-A-3,910,285. However, the system of this document has serious disadvantages. In fact, first of all, it requires comprehensive modification of the associated pneumatic brake booster, since the pressure applied to the brake fluid is generated by the master cylinder which thus simulates a depression of the brake pedal by the driver. Moreover, in the anti-lock system, the brake fluid recovered in the expansion phase is sent directly to the reservoir, thus implying that, in the event of a failure of the associated pump, there is no longer any means of braking the vehicle, except to release the pedal to ensure the resupply of the chambers of the master cylinder and then to redepress this pedal, this being substantially contrary to the normal reflex of even a skilled driver.